Acrylic latices used in the production of printing inks often contain what is called a support resin. These water and alkaline soluble (at pHs about 8) resins are added to the emulsion polymerization reaction to improve the stability and rheological properties of the latex. Improved stability results from adsorption of the resin on the surface of the particles and the increased viscosity of the emulsion.
High molecular weight emulsion polymers are widely used in the coatings industry. However, several problems are associated with high molecular weight emulsion polymer technology, including: poor wetting of metal substrates, cratering of resulting films, low gloss or mudcaking of resulting films, wetting and adherency problems, mechanical instability, freeze-thaw instability, shear thinning, and poor physical properties of the resulting film. U.S. Pat. No. 4,839,413 (which is hereby incorporated by reference) attempts to address and overcome these problems by employing hard acrylic resins as support resins.
Such hard acrylic resins have become the support resins most commonly used by the ink industry. However, as these resins are relatively expensive, ink formulators are actively searching for low cost alternatives. Therefore, it is the object of this invention to utilize low cost alkali-soluble support resins to produce emulsion polymer compositions with improved mechanical and physical properties.